The denial-of-service attack resulted in thousands of emails flooding the broking site, prompting a cessation of services from Christmas Eve to the New Year period.

According to a Fairfax report, offshore Etrade clients were the worst affected with some countries unable to access accounts for almost two weeks. An ETrade spokesperson confirmed that while overseas clients were , more profoundly affected, Australian clients had intermittent access to their accounts.

"We experienced some malicious activity that impacted the performance of the ETrade website prior to Christmas," the ETrade spokesperson said in a statement.

"We responded immediately to minimise any disruption to our clients and ensure our data remained secure. At no stage was security of the ETrade site breached," it added.

Neither ANZ nor ETrade have supplied any detail on the nature of the attack or who the culprit was.

Customers only received an explanation of the outage yesterday stating, "immediate action was taken to restrict access from some overseas locations, but given the nature of the incident we were restricted in what we could communicate with you at the time. Importantly, at no stage was the security of the Etrade website breached."

The Sydney Morning Heraldreported that St George customers were also affected by the attack as its online trading service is supplied by Etrade. ®